The present invention relates to UV curable hardcoat compositions which are useful for imparting abrasion resistance and improved weathering resistance to thermoplastic substrates when applied and cured thereon. More particularly, the present invention relates to UV curable mixtures of a monofunctional branched or carbocyclic acrylate, such as isobornyl acrylate, which is used in combination with hexanediol diacrylate, colloidal silica, the hydrolysis product of an alkoxysilyl acrylate and an effective amount of a UV photoinitiator.
Prior to the present invention, as shown by Olson et al, U.S. Pat. No. 4,455,205, acrylic monomer, such as hexanediol diacrylate was utilized in combination with a UV photoinitiator, colloidal silica and an alkoxysilyl acrylate of the formula, ##STR1## where R is a C.sub.(1-13) monovalent hydrocarbon radical, R.sup.1 is a C.sub.(1-8) alkyl radical, R.sup.2 is a divalent C.sub.(2-8) alkylene radical, R.sup.3 is a monovalent radical selected from hydrogen and a C.sub.(1-8) alkyl radical, a is a whole number equal to 0 or 1, b is an integer equal to 1 to 3 inclusive, c is an integer equal to 1 to 3 inclusive, and the sum of a +b +c is equal to 4. Although the UV curable hardcoat compositions of Olson et al have been found to provide adherent and abrasion resistant coatings on thermoplastic substrates when cured, and the cured coated articles have been found to have improved weathering resistance, additional hardcoat compositions having increased abrasion and weathering resistance are constantly being sought by the plastics industry.